The present invention is directed to a polyurethane foam body with an alkaline substance suspended therein, as disclosed in U.S. Pat. No. 3,923,311. In said patent, there is disclosed a joint filler for sealing and protecting pipe joints, especially joints with exposed metal portions of two pipes forming the joint.
The joints formed by interconnecting the ends of a first and a second pipe are subject to corrosion due to water attacking the exposed metal portions of the steel end rings of the pipes. In the first pipe, the steel end ring is constituted by a spigot having a groove formed therein for the mounting of a rubber gasket. The steel spigot ring is mounted about the end of the first pipe which is of smaller diameter than the remainder of the pipe so that it may be received telescopingly within an end of the second pipe. The second pipe has, in turn, an opening formed in its respective end which is provided with a steel bell ring which is mounted in the wall of the opening and defines a bell face. The opening with the steel bell ring therein is of slightly greater diameter than the end of the first pipe with the steel spigot ring mounted thereabout so that as the end of the first pipe is forced into the end of the second pipe, the rubber gasket is compressed by the bell flare to provide thereby a tightly sealed joint.
As the steel spigot ring is forced into the opening of the second pipe, the annular portion of the end of the second pipe or bell face forces the polyurethane foam body with an alkaline substance suspended therein into a compressed state. The polyurethane foam body also is mounted about the steel spigot ring but rearwardly of the rubber gasket. The polyurethane foam body rests against a shoulder of the first pipe so that as the bell face of the second pipe compresses the polyurethane foam body, it is forced radially outwardly at the same time as it is compressed inwardly. Due to the fact that the polyurethane foam body has an alkaline substance such as portland cement suspended therein, protection of the exposed metal surfaces of the pipes is achieved. The protection arises due to hydration of the alkaline substance by the surrounding water, which releases the alkaline substance over a period of time from the polyurethane foam. The alkaline substance is dispersed in the polyurethane foam body in a manner as disclosed in the above-mentioned patent. This patent also sets out in greater detail the precise composition of the mixture.
It has been found, however, with the above system that in use for protecting the joints of small-diameter pipes, the resilient forces exerted by the polyurethane foam body on the steel bell ring end of the second pipe are so great as to cause the kickback thereof and the eventual separation of the pipes.